Chapter 8:
Bacterial Pathogens

Affiliations: 1: Laboratory for Infectious Disease Research, University of Missouri, Columbia, Missouri;
2: Laboratory for Infectious Disease Research, University of Missouri, Columbia, Missouri;
3: Laboratory for Infectious Disease Research and Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri;
4: Laboratory for Infectious Disease Research and Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri

Bacterial endotoxins are heat-stable components of the Gram-negative outer membrane that are released after a bacterial cell lyses and are also continuously shed by viable bacteria. Endotoxins cause systemic inflammatory responses and are associated with sepsis as well as chronic inflammation (1). The outer membrane of Gram-negative bacteria is covered up to 75% by lipopolysaccharides (LPSs); the remainder consists of proteins that primarily serve as channels for the entry and exit of molecules or as structures that mediate interactions with the environment (2). A LPS is composed of three parts—lipid A, core polysaccharide, and a glycan, typically O antigen. Lipid A is the ligand that stimulates inflammation by binding to receptors on the host cell surface as well as intracellular membranes and cytoplasm (3). Many bacterial pathogens, such as Francisella, Yersinia, Brucella, and Coxiella, synthesize an alternative form of lipid A that is less stimulatory in the mammalian host and significantly dampens the early host inflammatory responses, thus facilitating the establishment of disease.

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